<!DOCTYPE html>
<html reftest-async-scroll
      reftest-displayport-x="0" reftest-displayport-y="0"
      reftest-displayport-w="800" reftest-displayport-h="2000"
      reftest-async-scroll-x="0" reftest-async-scroll-y="50">
<style>
body {
  height: 4000px;
  margin: 0;
  overflow: hidden;
}
#sticky {
  position: sticky;
  top: 25px; /* scrolls regularly until the top edge hits 25px, then stays fixed */
  margin-top: 50px;
  height: 1200px;
  border-bottom: 1px solid black;
}
#fixed {
  position: fixed;
  top: 50px;
  left: 50px;
  width: 100px;
  height: 100px;
  box-sizing: border-box;
  border: 1px solid blue;
}
</style>
<div id="sticky">
  <div id="fixed"></div>
</div>
</html>
